The present disclosure relates to systems and methods for controlling humidity, and more particularly to controlling humidity of a working fluid provided by compressed air storage systems to mission critical applications.
Mission-critical applications such as data centers, server rooms, and other facilities housing sensitive electronics generally require reliable backup energy and cooling systems. Such applications may require a continuous and uninterrupted supply of power during periods of normal operation (e.g., the period of operation in which primary or utility power is available) and backup operation (e.g., the period of operation in which primary or utility power is interrupted, even if such interruption lasts a fraction of a second). In addition, such applications may require cooling during both normal and backup modes of operation to, for example, ensure optimal operating efficiency and/or to prevent equipment damage (e.g., by overheating).
During the normal mode of operation, primary or utility power may power a cooling system for cooling the mission critical application. However, during an interruption of primary power, one or more backup systems are needed to provide power and/or cooling for the mission critical system. Several systems are known for supplying uninterruptible power and cooling. For example, compressed air storage (CAS) systems and thermal and compressed air storage (TACAS) systems may provide backup power, including uninterrupted backup power when outfitted with transient power supplies, and cooling to mission critical applications.
CAS and TACAS systems utilize energy stored in compressed gas (or sometimes referred to as a working fluid) to generate power. Power is generated when the compressed gas drives a turbine, which in turn drives an electrical machine (e.g., a generator), which may produce the power. Examples of CAS and TACAS systems for generating power may be found in U.S. patent application No. 2004/0148922, the disclosure of which is hereby incorporated by reference herein in its entirety.
CAS and TACAS systems may take advantage of Joule-Thompson expansion of gas to obtain cooling in the form of cold gas by expanding the compressed gas. The compressed gas may be expanded at one or more points in the system, thereby enabling the system to route cold gas as desired. For example, the cold gas can be used to provide cooling for mission critical applications or for cooling various components or subsystems of the CAS and TACAS systems.
In addition to Joule-Thompson expansion gas, an adiabatic expansion (or nearly adiabatic expansion) of gas may occur as the compressed gas expands across the turbine. The expanded gas being discharged from the turbine may be used to cool a mission critical application.
While backup energy systems are available to provide backup power and/or cooling, it is desirable to provide greater control over the climate in which the mission critical application resides. For example, it may be desirable to precisely control the humidity in addition to the temperature of an enclosure housing a mission critical application. Maintaining the enclosure within an optimal range of humidity may be necessary to avoid damage to electronic equipment. For example, an above-optimal level of humidity may corrode circuitry or result in short circuits, which can result in malfunctions and equipment failures. A below-optimal level of humidity may promote an environment of enhanced static electricity, which may interfere with equipment operation and potentially lead to static discharges that can render electronic circuitry inoperable.
Approaches for ensuring dry gas is transmitted from a source of compressed air to the turbine in CAS and TACAS systems are known. For example, when gas is compressed and stored, it may pass through one or more driers or desiccant to remove moisture from the compressed gas. The removal of moisture may be necessary to prevent freezing of valves (e.g., regulators, flow-control valves, and solenoid valves) and wear of components in the flow stream caused by liquid droplets or ice particles flowing through the system. Though such approaches are effective for protecting against improper operation and component damage, such approaches may result in gas that is too dry for use in mission critical applications.
Accordingly, in view of the foregoing, it is desirable to provide systems and methods for controlling humidity of a working fluid used to provide climate control of a mission critical application.